What is the Goniometer app?
Goniometer is a digital goniometer app for iPhone. It turns the iPhone's motion sensor into a clinical-style goniometer so you can measure joint range of motion (ROM) in seconds — place the phone against the limb, read the live angle, and lock it when steady. It covers 47 movements from the cervical spine to every finger.
Can an iPhone measure range of motion?
Yes. The app reads the iPhone's device motion sensor, gravity-referenced like the built-in Level, to compute the joint angle. Smartphone inclinometer measurement has been shown valid and reliable for joint range of motion in peer-reviewed research (Keogh et al., systematic review, PLOS ONE, 2019).
Is the Goniometer app accurate?
It uses gravity-referenced device motion with a stability indicator so you only lock a steady reading, and normal-range reference values follow AAOS. Validity and reliability of smartphone inclinometry for ROM are supported in the peer-reviewed literature. Goniometer is an educational and reference tool, not a medical device.
Who is it for?
Occupational and physical therapists, hand therapists (CHTs), chiropractors, physicians and other doctors, nurses, athletic trainers, ATPs, and students — plus patients tracking their own range of motion and recovery at home. Anyone who needs to measure or document joint motion.
Is there a free goniometer app?
Yes — Goniometer: Range of Motion is a free goniometer app for iPhone. Measuring is free and unlimited for all 47 movements, with guided placement, AAOS normal ranges, the Quick Angle tool, one saved patient profile, and watermarked PDF & CSV export. Only the documentation layer (unlimited profiles, progress history, goal tracking, watermark-free letterhead reports) is a one-time Pro purchase — with a free trial (your first 8 saved readings).
How much does it cost?
Measuring is free and unlimited — every joint and movement, plus the Quick Angle and Level tools, your first patient profile, watermarked PDF & CSV export, and Face ID lock. Goniometer Pro is a one-time $14.99 purchase (no subscription) that adds unlimited patient profiles, progress history with trend charts, per-movement goal tracking, Total Active Motion, side-to-side comparison, watermark-free reports with your clinic letterhead, and hands-free auto-lock. You can try all of Pro free for your first 8 saved readings.
Is there a free trial?
Yes. You can try every Pro feature free for your first 8 saved readings, started from inside the app — no credit card and no auto-charge. When the trial ends, Pro simply locks again until you choose to unlock it with the one-time $14.99 purchase. Your saved measurements and patient profiles are never deleted.
What joints can it measure?
Cervical spine, shoulder, elbow, wrist, hip, knee, and ankle, plus every finger and thumb joint (MCP, PIP, DIP, and thumb MCP/IP) — 47 movements in total, each with an animated placement guide.
Who makes Goniometer?
Goniometer is built by Kevin Lan, OTR/L, ATP — a licensed occupational therapist and assistive technology professional with 8+ years of clinical experience — and designed around real clinical workflows: guided placement, AAOS reference values, and documentation-ready exports.
Is my data private?
Yes. Goniometer collects no data — no accounts, no analytics, no tracking. Measurements and patient profiles stay on your device, encrypted at rest, and the app works fully offline. The App Store privacy label is "Data Not Collected."
Is Goniometer HIPAA compliant?
No app can be "HIPAA certified" — no such certification exists, and compliance is an obligation of the clinician or facility, not the software. Goniometer is designed to support your compliance: patient data never leaves the device, is encrypted at rest, can be locked behind Face ID at no cost, and is never transmitted to anyone — so there's no BAA to sign. See what HIPAA actually requires of a goniometer app.
